Thursday, January 24, 2013

The Birds and The Bees... Chicken-Style

I think it is time we had "The Talk". You've kept chickens for a while. You know that the roosters fertilize the hens. You know that when a hen goes broody, those fertilized eggs might just hatch out into little fluffy chicks if you let her set on them a while. Perhaps, you have even hatched chicks yourself in an incubator environment. But, have you ever wondered how that process takes place? If you were one of my children, this talk would start with, "When a Mommy and a Daddy love each other very much..." but, I think we'll skip that part and begin with some important definitions for you to know. Pay close attention, there might be a quiz later.

Definitions You Should Know:

Ovary: is a cluster of developing yolks. It is fully formed at hatching, but it remains very small until the hen reaches maturity at about 5 months of age. Hens are hatched with all the potential yolks of the eggs she will ever produce during her life time.

Oviduct: is the long tube that is divided into 5 major sections: infundibulum, magnum, isthmus, shell gland, and vagina.

Infundibulum: is the first part of the oviduct. The yolk is enveloped by the muscular infundibulum for about 15 minutes. Fertilization takes place here.

Magnum: is the second part of the oviduct. The yolk stays in the magnum for about 3 hours while the thick white albumen is attached to the yolk.

Isthmus: is the third part of the oviduct. It is here that the inner and outer shell membranes are added to the yolk. This takes about 75 minutes.

Shell Gland (Uterus): is the fourth section of the oviduct. The shell is placed around the egg here and pigment is applied. The egg remains in here for about 20 hours.

Vagina: this last section of the oviduct does not really play a part in creating the egg, but it hosts the muscles responsible for pushing the egg out of the hen's body.

Sperm Host Glands: These are located near the junction of the vagina and the shell gland. Sperm can be held alive for up to 2 weeks in this gland. When an egg is laid, if there is sperm stored, some of it will be squeezed out of the gland into the oviduct. From there, the sperm "swim" towards the infundibulum where fertilization takes place.

Albumen: is the "white of the egg". It's full of protein and provides nutrition for an embryo.

Shell Membranes: a pair of membranes lining the inner surface of an egg shell. They are designed to allow easy entry of oxygen but to prevent evaporation.

All put together, it looks like this:
Image used from site.
Original image from John Anderson, Dept. of Animal Sciences, The Ohio State University

If you have a rooster in your flock, chances are you have seen them perform their mating dance for the hens. If the hen is willing, she will crouch down and allow the rooster to mate. It is common for roosters to bite a hen's comb or neck feathers to maintain his balance during this momentary balancing act. This does not usually injure a hen, though multiple matings in a short period of time can cause problems. Our rooster, Sebastian, will also fan out his feathers like a cape around the hen he is courting. Sometimes, the hen is not willing. I have seen my hens chase off a rejected rooster, occasionally puffing up and going toe to toe with the lad she has deemed undesirable until he gets the point and retreats. I have also seen roosters unwilling to accept rejection, sneak up on an unsuspecting hen and have his way, regardless of her preference.

However the mating occurs, the rooster's sperm remains in the hen's sperm host gland, alive and viable for up to 2 weeks. If sperm is stored here, any eggs produced will most likely become fertile. When a fertile egg is laid, if it is kept warm, it will begin its development into a chick. If an unfertilized egg is laid, it will never develop into a chick. Hens lay eggs approximately every 26 hours. In this way, a typical hen will lay an egg every day for about 6 consecutive days and then skip a day, laying the eggs later and later in the day, as the cycle progresses. 
How does an egg develop inside the hen?

First, a yolk is released from the hen's Ovary. It travels through the Oviduct. The first stop is in the muscular Infundibulum where it is surrounded and any fertilization takes place. Next, the yolk moves on into the Magnum, where the white albumen is attached to it. The inner and outer shell membranes are attached in the Isthmus. This takes about 75 minutes to occur. Then, the egg travels to the Shell Gland (Uterus) where the shell is placed around the egg and any pigment (the coloration of the egg) is applied. The egg remains there for about 20 hours until the Vagina contracts and expels the egg out of the hen's body.
I found tons of useful information for writing this post from the University of Kentucky Fact Sheet. It is a very informative 5-page document with excellent pictures. I highly recommend it to chicken- keepers, home-schoolers, and 4-H clubs. You might also be interested in this post: Marvelous Creation, which discusses the process of how fertilized eggs develop into chicks.

Thanks for stopping in for a visit with us today.
Sean and Sonja ♥

Check out the Hops: Home Acre Hop #5 and Farm Girl Farm Fest #19


  1. Thank you for this wonderful information. The miracle of life is awesome!

  2. What a wonderful, informative post! I had absolutely no idea that sperm could be held for up to 2 weeks and would fertilize the eggs. I have always wondered that so thank you for enlightening me! Such a cool post :)

  3. Love this post and the information in it! And the title is just perfect lol.

  4. Very interesting. It really is amazing!

  5. Thanks so much for sharing this on The HomeAcre Hop! Great information! When I butcher my old hens I can see the eggs in various stages. It's pretty interesting.

  6. Do you have a print option on your site? This was excellent.

  7. I just found you today from Fresh Eggs Daily on FB. They recommended you and I am glad they did.I hope you are staying warm today. This article answers lots of my questions! I figured I was pretty close to understanding this but can't believe how many people don't get it, lol. Thank you for a great explanation. :)

  8. My goodness. I am 59 years young and had NO idea how the chicks were produced. Thought it was about time I learned. Thank you!

    1. Glad to have been helpful. :) Thanks for visiting with us. ~Sonja ♥